The invention relates to a device for generating picture information in real time for testing picture resolving sensors, in particular for testing infrared sensors in target tracking seeker heads.
It is known to test picture resolving infrared sensors dynamically by means of simulated object scenes. This is done in so-called HIL-installations (Hardware-in-the-Loop). In such installations, the flight of a target tracking missile is simulated from the launching up to the approach to the target. By the seeker head, tis is viewed as a "picture explosion". A simulated object as viewed by the seeker head becomes larger and larger during the approach. The sequence of scenes occurring during the flight has to be simulated in real time, i.e. at a frame sequence frequency which permits quasicontinuous representation.
When representing the object or target scene in the infrared spectral range, as required for infrared target tracking seeker heads, high resolution is required. The simulation has to permit representation of high dynamic range of the radiation levels in the individual picture elements (pixels). The radiation levels have to be able to vary within a large range. Typically, the maximum radiation level which can be represented in an object scene should be higher by a factor of 2000 than the minimum radiation level which can be represented. It must be possible to build up and to remove the radiation levels within few milliseconds, this applies also to the high radiation levels. It may well be that the maximum radiation level lies directly adjacent to the minimum radiation level. Therefore, avoiding cross-talk is of particular importance. Such strong variations of the radiation level are, in particular, required for the representation of disturbing radiation emitters (flares).
In addition, the representation of quickly variable or movable objects such as modulated disturbing radiation emitters (jammers) or of rotor blades of helicopters requires high dynamic range in time, i.e. low time constants during rise and decay of the radiation.
Infrared scene simulators are known, wherein the picture information in the infrared spectral range is generated by pointwise heating resistors and foils. In the prior art devices of this type, however, the dynamic range of the signal levels and time constants, which can be represented in this way, by no means reach the demanded values. Also there is undesirably strong cross-talk. The heat energy for generating the infrared radiation is produced within the picture matrix representing the object scene. This heat energy dissipates across the picture matrix. This results in interfering cross-talk signals. In the prior art scene simulators, these cross-talk signals have to be damped down by expensive and heavy cooling devices. This makes it difficult to mount the infrared scene simulator on a target movement frame as usually provided in HIL-installations.
Furthermore, it is known to generate the picture information by a laser, the light beam of which carries out a two-dimensional sweeping movement. To this end the light beam is directed to be reflected by a mirror system. Such a mirror system has to be very quick. Therefore, the mirror system is quite expensive. Also here, the dynamic range of the radiation levels which can be represented is limited. The syncronisation of the movements of the light spot generated by the light beam with the target tracking seeker head to be tested presents problems.
EP patent application 0,469,293 discloses a bistable, deformable mirror array which is composed of individual, pixel-like mirror elements. The individual mirror elements are pivotally mounted and arranged to be tilted by control signals into first or second positions.